1. Field of the Invention
The present invention relates to a vehicular illumination lamp which utilizes a light emitting device as a light source.
2. Related Art
In recent years, vehicular illumination lamps, which utilizes light emitting devices such as light emitting diodes as light sources, have been proposed for use as headlamps or the like.
For example, Japanese Patent Publication No. 2003-317513 (“JP '513”) describes a so-called projector type vehicular illumination lamp, which includes a projection lens disposed on an optical axis that extends in a longitudinal direction of the lamp and a light source unit disposed rearwards of the projection lens. The light source unit described in JP '513 is configured so as to include a light emitting device disposed near the optical axis at a position situated further rearwards than a rear focal point of the projection lens, a reflector disposed in such a manner as to cover the light emitting device from thereabove so as to reflect light from the light emitting device towards a front of the lamp while causing the light to get closer to the optical axis, and a mirror member having an upwardly oriented reflecting surface, which extends rearwards substantially along the optical axis from near the rear focal point so as to reflect part of reflected light from the reflector upwards. Then, a light distribution pattern having a cut-off line as an inversely projected image of a front end edge of the upwardly oriented reflecting surface at an upper end thereof is formed when the light source unit is turned on.
When using a lamp configuration such as that described in the aforesaid JP '513, it is possible to form a light distribution pattern having a clear cut-off line at an upper end portion thereof while enhancing the utilization factor of a bundle of rays of light from a light emitting device.
In such a lamp configuration, however, since only a light distribution having a cut-off line can be formed, the lamp configuration is only suitable for a lamp for forming a lower beam light distribution pattern of a headlamp. Accordingly, it is necessary to provide another separate vehicular illumination lamp in order to form a upper beam light distribution pattern for the headlamp.
In addition, if a vehicular illumination lamp that which utilizes a light emitting device as a light source, is used as a headlamp, it is preferable to use a plurality of such vehicular illumination lamps in order to provide a predetermined brightness. However, in the event that the vehicular illumination lamps so used have different lamp configurations for lower beam and upper beam, there is a problem that many vehicular illumination lamps are needed to meet the requirements.
The invention was made in the light of these situations, and an object thereof is to provide a vehicular illumination lamp utilizing a light emitting device as a light source which can form a light distribution pattern having a cut-off line at an upper end portion thereof and another light distribution pattern which spreads on an upper side of the cut-off line while enhancing the utilization factor of a bundle of rays of light from the light emitting device.